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Burgess Shale provides evidence of evolutionary leaps

“The Burgess Shale adds to evidence that evolution proceeded with bouts of rapid diversification interspersed with extinctions,” says this article in the Smithsonian, thus bolstering my contention that evolution does take leaps.

The Burgess Shale, in the Canadian Rockies some 50 miles west of Banff, is riddled a rich variety of organisms that thrived some 520 to 540 million years ago during the Cambrian Explosion.

Though the Burgess Shale stands almost 7,500 feet above sea level, during the Cambrian Period it lay beneath the sea near the Equator.

Underwater avalanches of fine mud periodically engulfed the area, instantly killing all sorts of organisms and preserving exceptionally fine details of their structures.

Artist's conception of Opabinia on the ocean floor

Some of those details show organisms that had never before existed on the face of the earth. “Weird wonders,” the late evolutionary biologist Stephen Jay Gould called them.

Opabinia had five eyes – count ’em, five! – How’s that for weird?

Some of the weird wonders “look more like plumbing devices, plastic hairbrushes or floor polishers than familiar creatures.” One, the three-foot-long Anomalocaris, boasted a mouth resembling a square, sharp-toothed nutcracker.

Here’s how I describe the Cambrian explosion in Magnetic Reversals and Evolutionary Leaps:

For all intents and purposes…life on earth began about 580 million years ago at the beginning of the Cambrian Period, when new life suddenly exploded across the earth. A dizzying array of new organisms appeared in the geologic record as if from nowhere. An astonishing burst of shelled forms took place, and virtually all major forms of animal life, including the ubiquitous trilobite, suddenly appeared. (Trilobites were distant cousins of today’s horseshoe crab.)

Called the Cambrian explosion, the abrupt change from simple life-forms to more advanced was a critical turning point in the history of life. No one knows how or why it happened. What we do know is that the pattern has always been the same—sudden—always sudden. (p.24)

Nature does take leaps

“Most new species appear with a bang, not a protracted crescen­do,” said (Stephen Jay) Gould. “Gradualism is not a fact of nature. A species seems to remain unchanged in the fossil record for millions of years, before abruptly disappearing, only to be replaced just as rapidly with a species that is, though clearly related, substantially different. Nature does take leaps.” (p.21)

Their fossils show that “a lot of evolution’s early experiments failed to survive in the long term,” says Maglaty.